Device for applying to a substrate a liquid medium which is exposed to UV radiation

ABSTRACT

An apparatus includes a housing having an elongated chamber, an inlet opening extending into the chamber, and a slit shaped outlet opening. A tube element extends in a longitudinal direction through the chamber and is at least partially transparent to UV radiation. The tube element is arranged in the chamber such that a flow space is formed between the tube element and the wall of the chamber. At least one UV-radiation source in the tube element is arranged to emit UV-radiation in the direction of the flow space and through the outlet opening out of the housing to generate radicals in the liquid and bring the radicals to the substrate surface. Means are provided for adjusting the radiation exiting the outlet opening through the tube element such that the intensity of the radiation increases towards the longitudinal center plane of the chamber.

RELATED APPLICATIONS

This application corresponds to PCT/EP2018/055103, filed Mar. 1, 2018, which claims the benefit of German Application No. 10 2017 203 351.7, filed Mar. 1, 2017, the subject matter of which are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus for applying a liquid medium irradiated with UV radiation onto a substrate in order to treat the substrate, wherein the liquid is locally applied in the region of the apparatus to a partial area of the substrate and wherein UV radiation is introduced into the liquid.

In semiconductor technology, it is known that for example photomasks have to be exposed to different treatment steps, in particular cleaning steps, both during their production and during their use. For example, it is known to expose the photomasks to a wet cleaning, in which at least locally a liquid film is formed on the substrate and UV radiation is introduced into this liquid film. Corresponding cleaning steps are also known for semiconductor wafers during their manufacture. In this case, the liquid and the UV radiation are matched such that a majority of the UV radiation is absorbed in the liquid film in order to generate radicals in the liquid film, which promote the cleaning. In particular, it is known to generate hydroxyl radicals in for example diluted hydrogen peroxide water or ozone water O₃—H₂O. Such hydroxyl radicals cause selective dissolution of organic materials from the substrate surface without harming metallic layers on the substrate surface if they are present. A portion of the radiation introduced into the liquid is typically not absorbed and impinges onto the substrate itself. Both the intensity of the radiation impinging onto the substrate as well as the concentration of radicals at the substrate surface substantially contribute to achieving a certain process result, such as a resist strip.

Typically, in such a wet treatment, an application unit for the liquid, via which also UV radiation is introduced into the liquid, is moved over and across the substrate such that the liquid sweeps over the substrate. Treatment with radical is primarily carried out below the application unit, as the radicals rapidly disintegrate when the application unit continues to move and areas which had just been irradiated with UV radiation are no longer irradiated with UV radiation. Therefore, a treatment of the substrate surface occurs in a small treatment area underneath the application unit.

An apparatus suitable for this purpose is, for example, known from German patent application DE 10 2009 058 962 A1 of the same applicant as the present application. In particular, the application shows an apparatus according to the preamble of claim 1. In the known design, a high concentration of radicals is formed in a longitudinal central area below an outlet opening of an application unit, which concentration, however, rapidly decreases in the direction transverse to the outlet opening.

Next to the wet treatment there is also known a dry treatment, in which UV radiation is introduced into a dry gas, such as O₂, or into a mixture of a dry gas and vapor, for example N₂+H₂O, the dry gas or the mixture being directed onto a substrate. The photolysis reactions occurring during the dry treatment substantially differ from the reactions occurring during the wet treatment and are substantially less complex and proceed faster than in the wet treatment. The techniques used in the different treatment regimens may thus not be easily exchanged.

SUMMARY OF THE INVENTION

In view of an apparatus according to the above application, it is an object of the present application to homogenize a treatment, such as for example a resist strip, over the treatment area of the apparatus. The present invention is distinguished over the device of the above-mentioned German patent application DE 10 2009 058 962 A1 by the additional features of the characterizing portion of claim 1.

In particular, there is provided an apparatus for applying a liquid medium irradiated with UV radiation onto a substrate, the apparatus comprising: a housing having an elongated chamber, at least one inlet opening, which opens into the chamber, and at least one slit shaped outlet opening opposite the inlet opening, which extends over the length of the chamber, a tube element, which extends in a longitudinal direction through the chamber, the tube element being at least partially transparent to UV radiation, wherein the tube element is arranged in the chamber such that a flow space is formed between the tube element and the wall of the chamber, the flow space being symmetric with respect to a longitudinal center plane of the chamber, the longitudinal center plane dissecting the outlet opening in its middle, and such that the tube element extends into the slit shaped outlet opening in the housing and thereby forms two longitudinally extending outlet slits between the tube element and the housing, and at least one UV-radiation source in the tube element, which is arranged to emit UV-radiation in the direction of the flow space and through the outlet opening out of the housing to generate radicals in the liquid and to bring the same to the surface of the substrate. The apparatus is distinguished by means for adjusting the radiation exiting the outlet opening through the tube element such that the intensity of the radiation increases towards the longitudinal center plane of the chamber. Such an apparatus is capable to at least partially compensate for a reduction of radicals towards the longitudinal center plane by means of an increase in the intensity of the radiation, to thereby increase the homogeneity of a process reaction, such as a lacquer or resist strip, over the width of the outlet opening.

In one embodiment, the tube element has a round cross section and the means comprise at least one optical element arranged to vary the intensity of the radiation exiting through the outlet opening and the tube element such that the intensity increases, in particular steadily increases towards the longitudinal center plane of the chamber. As a result, in a particularly simple manner, a good distribution of the liquid on the substrate and a desired distribution of the radiation may be achieved. The at least one optical means may comprise at least one mirror element which is arranged at a side of the at least one radiation source opposite from the substrate and/or adjacent the radiation source and which reflects radiation in such a way toward the outlet opening that the above distribution of the intensity is achieved. Preferably, the mirror element is symmetrical with respect to the longitudinal center plane of the chamber. In a preferred embodiment, the mirror element at least partially encompasses the at least one radiation source, such that the emission of the radiation source may be primarily directed towards the outlet opening.

For a simple construction of the apparatus and a desired intensity distribution, the at least one radiation source is preferably arranged on the longitudinal center plane of the chamber and below a transverse center plane of the tube element, which extends perpendicular to the longitudinal center plane of the chamber and which dissect the tube element in the middle. As such the radiation element is shifted towards the outlet opening.

In one embodiment, the mirror element is at least partially arranged below the transverse center plane of the tube element in order to direct manly radiation from the lower portion of the tube element out of the housing.

In a further embodiment of the apparatus, the at least one optical means comprises a plurality of at least three UV radiation sources within the tube element, which are located adjacent to each other and adjacent to a portion of the tube element which is arranged in the outlet opening or outside the chamber, wherein the adjacent radiation sources emit UV radiation with different radiation intensities such that the radiation intensity increases towards the longitudinal center plane of the chamber. In this embodiment, at least one separating element may be provided in the tube element, which essentially blocks radiation of the plurality of UV radiation sources in the direction of the flow space, and is in particular reflective. Here, the term essentially means that at least 90% of the radiation of the plurality of UV radiation sources is blocked in the direction of the flow space.

In one embodiment, the apparatus has a first UV radiation source in the tube element, which is arranged to emit UV radiation primarily into the flow space, and at least one second UV radiation source, which is arranged to emit UV radiation primarily through the outlet opening, wherein primarily in this context relates to at least 80% of the intensity of radiation stemming from the respective radiation source and exiting the tube element.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in more detail herein below with reference to the drawings. In the drawings:

FIG. 1 shows a schematic top view of a substrate treatment apparatus having an apparatus according to the invention for applying a liquid medium irradiated with UV radiation onto a substrate;

FIG. 2 shows a schematic sectional view of the apparatus according to the invention along the line II-II in FIG. 1;

FIG. 3 shows a schematic sectional view taken along the line III-III in FIG. 4, which is similar to FIG. 2 but shows an alternative embodiment;

FIG. 4 shows a schematic longitudinal sectional view of a housing of the alternative embodiment of the invention shown in FIG. 3 along the line IV-IV in FIG. 3;

FIG. 5 shows a schematic perspective view of the housing of FIG. 4;

FIG. 6 shows a schematic top view of the housing of FIG. 4;

FIG. 7 shows a schematic front view of a clamping bracket;

FIGS. 8a and 8b show schematic horizontal sectional views, in the region of outlet slits of the apparatus according to the invention, which explain the effect of clamping brackets;

FIGS. 9a to 9c show schematic sectional views through different configurations of a radiation part of an apparatus of the above type;

FIGS. 10a to 10c show schematic sectional views of inventive alternative embodiments of the radiation part;

FIG. 11 shows a schematic sectional view through a further alternative configuration of the radiation part;

FIG. 12 shows a schematic sectional view similar to FIG. 11 of a further configuration of the radiation part.

DESCRIPTION

Directional references used in the following description, such as top or bottom, left or right, refer to the illustration in the figures and are not to be construed as limiting the application, although they may be preferred arrangements. In the following description, the term “bore” is to be understood as a longitudinally extending blind or through hole, which is independent of the manner of its manufacture, i.e. it does not have to be made by the process of drilling or boring, but can be manufactured in any suitable manner.

FIG. 1 shows a schematic top view of an apparatus 1 for a UV radiation enhanced wet treatment of substrates 2, in particular masks or semiconductor wafers for the chip production, wherein the substrate may also be one of the following: a photomask for the production of semiconductor wafers, a semiconductor wafer, in particular a Si-wafer, a Ge-wafer, a GaAs-wafer, a InP-wafer, a flat panel substrate, and a multi-layer ceramic ceramic substrate. FIG. 2 shows a schematic sectional view of the apparatus 1 along the line II-II in FIG. 1. The apparatus 1 comprises in substance a substrate holder 4 and an application unit 6. The substrate holder 4 and the application unit 6 may be accommodated in a pressure chamber, not shown, in which by suitable means an overpressure or a negative pressure can be generated.

It should be noted that in a wet treatment, a liquid, such as, for example, diluted hydrogen peroxide water or ozone water O₃H₂O or some other, in particular, water-containing liquid, is applied to the substrate. By irradiating the liquid with UV radiation, complex reactions occur and even if only water is used as a liquid, for example, 14 different species are generated, such as H₂O, H^(•), HO^(•), e-aq, HO₂ ^(•), O₂ ^(•−), H₂, O₂, H₂O₂, H₂O⁻¹, H₃O⁺, HO⁻, O₃ ^(•−) and HO₃ ^(•). Such reactions in a liquid are much more complex and radicals have much shorter lifetimes than reactions occurring in gases irradiated with UV radiation, and therefore, a wet treatment apparatus is not readily comparable to a treatment apparatus using gases. The reactions are wavelength-dependent and the direction of the reaction towards one or another species may be influenced by wavelength selection.

The substrate holder 4 is, as indicated in FIG. 1, shown as a flat rectangular plate for receiving the also rectangular substrate 2. However, the substrate receptacle 4 can also assume different shapes and be matched to the shape of a substrate 2 to be treated. The substrate holder 4 has at least one drainage, not shown, for liquid media, which can be applied to the substrate 2 via the application unit 6.

The application unit 6 consists of a main part 8 and a support part 10, which carries the main part 8 in a movable manner, as indicated by the double arrows A and B. In particular, the support member 10 has a support arm 12 which is connected at one end to the main part 8 while the other end is connected to a drive unit, not shown. As shown by the double arrows A and B, the drive unit may, for example, provide at least one of a pivotal movement of the support arm 10 and thus the main part 8 and a linear movement. As a result, the main part 8 can be moved in the desired manner over a substrate 2 accommodated on the substrate holder 4 in order to allow treatment of partial areas of the substrate or also of the entire surface of the substrate. In addition, it is also possible for the support arm 10 to perform a lifting movement in order to be able to adjust a distance between the main part 8 and the surface of a substrate 2 received on the substrate holder 4.

Furthermore, it is alternatively or additionally possible to provide a movement mechanism for the substrate holder 4 in order to be able to provide a relative movement between the substrate 2 and the main part 8.

The main part 8 in substance made up of a housing 14, media ports 16 and a radiation part 18. The housing 14 has an elongated cuboid shaped body 20 made of a suitable plastic, such as TFM, a modified PTFE. The housing may also be made of another suitable material. The material should be selected so that it is resistant to the temperatures and media being used. A longitudinally extending chamber 22 which extends over the entire length of the body 20 is defined in the body. At the longitudinal ends of the body 20 cover elements, which are not shown may be attached in order to delimit the chamber 22 in the longitudinal direction. The body 20 and thus the chamber 22 have a length which is greater than a width dimension of the substrate 2 in order to be able to apply a liquid medium over the entire width of the substrate 2, as will be explained in more detail herein below. It is, however, also possible that the body 20 or the chamber 22 has smaller dimensions. The inner wall 23 of the chamber can be formed such that it has a high reflectivity, in particular for UV radiation, whereas IR radiation is essentially absorbed.

The chamber 22 has a substantially round cross-section, while the chamber 22 opens toward the lower face or bottom of the body 20, so that the body 20 defines a downwards (towards the substrate 2) facing opening 21. Consequently, the inner wall 23 of the chamber 22 in section only describes a partial circle, which is larger than a semicircle, and preferably extends over an angular range of 250° to 300°, in particular over 270° to 290°.

In the upper region of the chamber 22, at least one supply line 24, which is fluidly connected to the port 16, is provided in the body 20, the supply line 24 being arranged directly opposite the opening 21. The supply line 24 is fluidly connected to the chamber 22 in order to be able to conduct a liquid medium into the chamber 22, as will be explained in more detail herein below.

In the plan view of FIG. 1, three ports 16 are shown, which can each be fluidly connected to the chamber 22 via a respective supply line 24. However, a larger or smaller number of ports can also be provided. Via the ports 16, a single liquid medium can be conducted into the chamber 22, or several media can be conducted into the chamber 22, which can be introduced simultaneously or sequentially. In particular, it is possible to connect different media sources to the ports 16, via which, for example, different media can be conducted simultaneously to the respective ports 16 in order to produce an in-situ mixture. In particular, liquids are considered for the media, but gases may also be supplied which, for example, are mixed with a liquid in the port 16 and the supply line 24 before they are introduced into the chamber 22.

The radiation part 18 is substance formed by a tube element 30 and at least one radiation source 32. The tube element 30 has an elongated shape and extends over the entire length of the chamber 22 and may extend through (or into) the cover members, not shown, at the ends of the body 20. The tube element 30 is made of a material which is substantially transparent to UV radiation and has a round cross-section. The center point of the tube element 30 having the round cross-section is offset with respect to the center point of the partial circle formed by the inner wall 23 of the chamber 22 in the direction of the opening 21. The tube element 30 extends partially through the opening 21 out of the housing 14, as shown in FIG. 2.

Thus, a flow space is formed between the tube element 30 and the inner wall 23 of the chamber 22. The flow space is symmetrical with respect to a longitudinal center plane C of the chamber 22 (see line IV-IV in FIG. 3) which centrally intersects the outlet opening 21 and the supply line 24. The flow space forms right and left branches, as shown in the cross-sectional view in FIG. 2. Each of the branches has at the lower end thereof an outlet slit 37, which is formed between the tube element 30 and the respective end of the inner wall 23 in the region of the opening 21. Starting from the supply line 24 and extending towards the respective outlet slit 37, each of the branches of the flow space has a tapering flow cross-section. In particular, the flow cross-section of the flow space in each branch continuously tapers in the direction of the respective outlet slit 37. The ratio of the flow cross section of the flow space in the area adjacent to the at least one supply line 24 and at the outlet slits 37 is in the range from 10:1 to 40:1 and preferably in the range from 15:1 to 25:1. Media flowing in the direction of the outlet slits 37 are therefore significantly accelerated. A respective acceleration of the media leads on the one hand to a homogenization of the flow and on the other hand to high flow velocities at the outlet slits 37. The high flow velocities promote the formation of a substantially continuous curtain of the liquid medium below the opening 21 which can be used to form a liquid film on a substrate 2 disposed thereunder.

In FIG. 2 flow arrows are indicated, which show a flow of a liquid medium from the port 16 via the supply line 24 and the chamber 22 out of the housing 14.

The radiation source 32 is—in the illustrated configuration—a rod-shaped lamp, which is arranged centrally within the tube element 30. The rod-shaped lamp 32 again extends over the entire length of the chamber 22 to provide a uniform distribution of radiation over the length of the chamber 22. The radiation source 32 primarily emits UV radiation in a desired spectral range, wherein the emitted radiation is emitted both into the flow space of the chamber 22 and through the opening 21 out of the housing 14. The radiation may be specifically selected for a specific purpose, as will be explained in more detail below. The radiation can also be controlled such that radiation emitted into the flow space is different to radiation emitted out of the opening 21.

Instead of or in addition to such a tubular radiation source, other radiation sources may also be provided, as shown in part in subsequent embodiments. In particular, more than one radiation source 32 can be provided within the tube element 30. For example, gas discharge lamps, but also LEDs or other suitable light sources which emit in a desired spectral range (at least also in the UV range) can be used as the radiation source 32.

The space 40 which is formed between the tube element 30 and the radiation source 32 can be supplied with a cooling medium, in particular a gaseous cooling medium to prevent overheating of the elements. In this case, the cooling medium is to be chosen so that it absorbs substantially no UV radiation.

A further embodiment of an application unit 6, in particular an alternative main part 108, which can be used in the device according to FIG. 1, will now be described with reference to FIGS. 3 to 8. The main part 108 has in substance a housing 114, a media guide 116 and a radiation part 118.

The housing 114 again has an elongated, cuboid shaped body 120 of a suitable material (such as TFM) having a longitudinally extending chamber 122 which extends over the entire length of the body 120. At the longitudinal ends of the body 120 covering elements (not shown) may be attached for delimiting the chamber 122 in the longitudinal direction. The covering elements may for example be attached by screws, which provides a releasable connection. However, other ways of connecting the covering elements, which are preferably releasable may be used instead. The chamber 122 may again have a length which is greater than a width dimension of a substrate 2, onto which a liquid medium is to be applied.

Again, the chamber 122 has a substantially circular cross-section, with the chamber 122 opening to a lower face or bottom 124 of the body 120 so as to define a downwardly facing opening 121. An inner wall 123 of the chamber 122 thus again describes a partial circle, which, however, is larger than a semicircle. The opening angle of the opening 121 is preferably in a range between 60° and 120°, ad is in particular between 70° and 90°.

The bottom 124 of the body 120 is configured to form a slope inclined upwards towards sidewalls 128 of the body 120. Between the slope and the opening 121, a substantially planar area is formed, and directly adjacent to the opening 121, the body 120 has a round edge 126. This round edge connects the substantially planar portion of the bottom 124 with the circular inner wall 123 of the chamber 122 and at its apex defines the actual opening 121 in the body 120.

In the transition region between the bottom 124 and side walls 128 of the body 120 a plurality of oblique recesses (e.g. 5 on each side, as shown) is provided. In the region of each of these recesses 130, the body 120 has a through-bore 132 to the chamber 122. The through hole 132 is stepped and has a wider region facing the recess 130 and a narrower region facing the chamber 122. In the wider region facing the recess 130, the through-bore 132 is provided with an internal thread. The respective through-bore 132 serves to receive an adjusting element 134, which has a stepped shape corresponding to the stepped shape of the through-bore 132. The adjusting element 134 has a head part 136 and an adjustment part 138. The head portion 136 is sized to pass through the narrow region of the through-bore 132 so as to be able to protrude into the chamber 122. The adjustment part 138 has an external thread engageable with the internal thread in the wider region of the through-bore 132 to be screwed therein. In this case, the depth of engagement of the adjustment part 138 determines how far the head part 136 of the adjusting element 134 projects into the chamber 122. The adjusting element 134 is made of a suitable material that is resistant to the temperatures and the media used and may have some resiliency. In particular, a PFA material (polyfluoroalkoxyl polymer material) has proven to be suitable. However, also other materials, in particular other plastic materials may be used.

A top side 140 of the body 120 has a plurality of recesses 142 extending transversely to the longitudinal direction of the body 120, which are aligned with the recesses 130 in the longitudinal direction of the body 120. In the area of each recess 142, a further recess 144 and a threaded bore 146 are provided. The threaded bore 146 serves to receive a screw, via which a cover plate 147 can be attached to fill the recess 142.

The recess 144 has a first section which extends at the bottom of the recess 142 transversely to the longitudinal direction of the body 120. The recess 144 further has sections extending directly adjacent to the respective side walls 128 in a direction parallel to the side walls 128 into body 120. The recess 144 thus forms in substance a U-shape, as best seen in FIG. 3.

The recess 144 serves to receive a clamping element 150, as best seen in FIG. 3. FIG. 7 shows a perspective view of the clamp member 150 in a non-installed and thus relaxed state. The clamping element 150 has in substance a U-shape, wherein (in the relaxed state) legs 152 of the U-shaped clamp member 150 extend from a base portion 154 of the clamp member 150 towards each other without touching each other. In other words, the distance between the free ends of the legs 152 is smaller than the distance of the legs at the base portion 154. Thus, when the legs 152 of the clamping element 150 are inserted into the U-shaped recess 144, they must be slightly bent apart and they then exert an inwardly directed bias onto the portion of the body 120 adjacent the legs. In particular, an inwardly directed bias is provided in the region of the adjusting elements 134.

The aforementioned media guide 116 is integrally formed in the body 120, and will be explained in more detail herein below. The media guide 116 is essentially divided into supply elements 160, a media distribution channel 162 and inlet channels 164.

In the illustrated embodiment, four supply elements 160 are provided, which are spaced apart in the longitudinal direction of the body 120. The supply elements 160 are not uniformly spaced. Rather, the distance between the middle supply elements 160 is smaller than the distance to their respective outer supply elements 160. The supply elements 160 are each formed on the top surface 140 of the body 120 and each have substantially a frusto-conical portion 166 extending upwardly from the top surface 140. Above the frusto-conical portion 166, there is provided an annular port 168 suitably adapted for connection to an external supply line. In the frusto-conical portion 166, a vertically extending through-bore 170 is formed. The through-bore extends completely through the frusto-conical portion 166 of the supply element 160 into the media distribution channel 162, which will be explained in more detail herein below.

The media distribution channel 162 is formed by a longitudinal bore 174 located centrally in the transverse direction of the body 120. The longitudinal bore 174 extends completely through the body 120 and is disposed between the top 140 surface and the chamber 122. In the end regions, the longitudinal bore 174 has widened sections 176, which can be closed by suitable end caps, not shown. The actual media distribution channel 162 is formed only by the central, unclosed portion of the longitudinal bore 174. Of course, as one skilled in the art will appreciate, it would also be possible for the longitudinal bore 174 to open only toward one end of the body 120 and thus has a widened section 176 only at this end, which can be closed in a suitable manner.

As can be seen in particular in FIG. 4, the longitudinal bore 174, which forms the media distribution channel 162, is in fluid communication with the bores 170 at four locations. Any medium introduced via the supply elements 160 can be introduced into the media distribution channel 162 at various locations and is then distributed in the longitudinal direction of the body 120 within the media distribution channel 162.

In a wall member 177 located between the media distribution channel 162 and the chamber 122, a plurality of through bores are formed, which fluidly connect the media distribution channel 162 and the chamber 122 and thus form the inlet channels 164. In the illustrated embodiment twelve inlet channels 164 are provided. The inlet channels 164 are arranged offset with respect to the bores 170 in the longitudinal direction of the body 120. Of course, a different number of inlet channels 164 may be provided. The inlet channels 164 are preferably evenly spaced in the longitudinal direction of the body 120, wherein a density in the range of 3/100 mm to 12/100 mm, in particular in the range of 4/100 mm to 10/100 mm is currently preferred to promote a homogeneous flow of media in the chamber 122.

In the side of the wall member 177 facing the chamber 122 two blind bores 178 (see FIG. 4) are provided, which each serve to receive a spacer 179 (see FIG. 3). The spacers 179 are made of a suitable material that is durable at the temperatures and the media used and has some resiliency. In particular, PFA can again be used here, as in the case of the adjusting elements 134. The spacers 179 each have a foot, not shown, to be received in a respective one of the blind bores 178 and a frusto-conical main part, which can be seen in FIG. 3.

The radiation part 118 of this embodiment will now be explained in more detail. The radiation part 118 has a tube element 180 and at least one radiation source 182. These have substantially the same structure as the tube element 30 and the at least one radiation source 32 according to the first embodiment. The tube element 180 has an elongated shape with a round cross section and is made of material that is substantially transparent to UV radiation. The tube element 180 is received in the chamber 122 so as to extend over the entire length thereof, and the center of the tube element 180, which has a round cross section, is offset with respect to the center of the partial circle of the inner wall 123 of the chamber 122 towards the opening 121. The round tube element 180 again extends partially through the opening 121 out of the housing 14. Again, a flow space 184 is formed between the tube element 180 and the inner wall 123 of the chamber 122, the flow space 184 being symmetrical with respect to a longitudinal center plane C of the chamber 122 which centrally intersects the opening 121 and the supply elements 160. The flow space 184 forms a right and a left branch, as can be seen in the cross-sectional view of FIG. 3. Each of the branches has an exit slit 186 at its lower end. Starting from the inlet channels 164 to the respective outlet slit 186, each of the branches of the flow chamber has a tapering flow cross-section. The branches taper in the same manner as in the first embodiment.

As can be seen in the view according to FIG. 3, the tube element 180 rests on the heads 136 of the respective adjusting elements 134, and contacts the spacers 179 on its upper side. The adjusting elements 134 and the spacers 179 thus provide a 3-point contact and thus define the exact position of the tube element 180 in the chamber 122. As can be seen, the width of the outlet slits 186 can be adjusted to a certain extent by the adjusting elements 134. The respective heads 136 of the adjusting elements 134 form point supports which do not substantially affect a flow of a medium around the heads, so that a substantially continuous media curtain can be formed in the region of the outlet slits 186. The radiation source 182 may be placed within the tube member 180 in the same manner as in the first embodiment.

The main difference between the embodiment of the main part 8 according to FIG. 2 and the second embodiment of the main part 108 according to FIGS. 3 to 7 is in the region of the media guide. While in the first embodiment a medium is introduced directly into the chamber 122 via the supply lines 24, in the second embodiment this occurs via the supply elements 160 into the media distribution channel 162 and then via the inlet channels 164 into the chamber 122. As a result, a more uniform distribution of the liquid medium in the longitudinal direction of the body 120 is achieved. In the region of the chamber 122, a more uniform flow is thus provided in the flow space 184. In particular, in combination with the tapering cross section of the flow space 184, a uniform flow can be achieved at the exit slits 186 to form a uniform liquid curtain.

Another difference is the use of the brackets 150, the adjusting elements 134 and the spacers 179, which, however, can also be used in a corresponding manner in the first embodiment. The clamps 150 function to provide an inwardly directed bias in the region of the chamber 122, as will be explained in more detail with reference to FIGS. 8a and 8 b.

When a liquid medium is introduced into the chamber 122 via the media guide 116, an outwardly directed pressure is generated on the inner walls 123 of the chamber. In particular in the widest region of the chamber 122, where the body 120 has a small cross-section, a respective pressure can lead to a deformation of the body 120 such that the width at the outlet slits 186 may increase. This applies, in particular, to a middle region in the longitudinal direction of the body 120, since at the ends the cover members (not shown) would counteract a respective deformation.

In particular, as is shown in FIG. 8a , for example the width of the outlet slit 186 could increase substantially in the central region, which would of course change a respective media outflow from the outlet slit 186. This would counteract a uniform distribution of media. By using the brackets 150, this can be prevented, as shown in FIG. 8b . The brackets 150, particularly in combination with the adjusting elements 134, can ensure uniform widths of the outlet slits 186. The brackets 150, in particular in combination with the adjusting elements 134 may also be advantageous, independently of a change in a flow cross-section of the flow chamber, in order to ensure a constant width of the outlet slits 186.

Different configurations of the radiation part 18 of the first embodiment will now be explained in more detail with reference to FIGS. 9 to 12. However, these configurations can be used in the same way in the second embodiment.

FIG. 9a shows a normal configuration similar to FIG. 2, having a tube element 30, which has a round cross-section, and a rod-shaped radiation source 32 arranged centrally in the tube element 30. Where appropriate, the same reference numerals are used in the following as in the first embodiment, wherein the different configurations can of course also be used in the second embodiment.

The housing 14 with chamber 22 and supply line 24 is indicated only schematically. Below this unit, a substrate 2 is shown schematically.

Below the schematic representation of the different configuration, two graphs are shown, wherein the upper graph represents a distribution of the concentration of radicals on the surface of the substrate 2 when a liquid medium, such as hydrogen peroxide (H₂O₂) or DI water, is supplied to the substrate via the supply line 24 while the radiation source 32 is operated. The lower graph indicates the achievable change of a lacquer layer thickness on the substrate in a cleaning process promoted by the radicals, wherein here a stationary process control is assumed, that is, the unit is not moved across the substrate, but is stationary. Both distributions are shown in normalized form.

As can be seen, the radical concentration has a large effect on the removed lacquer layer. Additionally, the radiation impinging onto the substrate also has an influence on the amount of removal of the lacquer layer, even though this is not shown in FIG. 9a . For example, a lower concentration of radicals, which would lower the amount of removal of the lacquer layer, may be compensated by an increase on the radiation impinging onto the substrate. This is not a linear relationship and it is not possible to compensate a very low radical concentration by a lot of light or radiation. Hence there is a limit for the compensation. The radical concentration is highest in the region of the longitudinal center plane of the chamber 22 (see dashed line) and strongly decreases outwards. Thus, the radical concentration on the surface of the substrate 2 greatly differs in a direction transverse to the chamber 22. The UV-radiation exiting the tube element is in substance evenly distributed and thus the amount of removal of the lacquer layer in substance follows the radical concentration.

FIG. 9b shows the same configuration as FIG. 9a , however, here ozone water O₃—H₂O is directed onto the substrate via the supply line 24, while the radiation source 32 is activated. Here, the graph of the radical distribution shows the highest concentration of radicals directly beneath the outlet slits 37 and the concentration decreases towards the longitudinal center plane. The UV-radiation exiting the tube element is in substance evenly distributed and thus the amount of removal of the lacquer layer again in substance follows the radical concentration. The inventors have realized that in such applications it would be beneficial to increase the intensity of light towards the longitudinal center plane to achieve a better homogeneity of the of lacquer removal (or a process result which is influenced in a similar manner).

FIG. 9c shows an alternative configuration, which is suitable to improve the homogeneity of a process result when a radical distribution as shown in FIG. 9b is present. Here, again a tube element 30 with a round cross-section is used. The radiation source 32 is again the same as previously described. The tube element 30 is modified such that it has different transmissivity characteristics in different regions. The tube element 30 has a first transmissivity in the region lying within the chamber 22 and another, second transmissivity outside the chamber 22. In particular, the first region has for example the highest possible transmissivity to UV radiation, that is, within the flow chamber substantially all of the UV radiation provided by the radiation source 32 can be introduced into the chamber 22.

On the other hand, the region of the tube element 30 located outside the chamber has a lower transmissivity due to increased absorption or reflection of UV radiation. In particular, the tube element 30 has the highest transmissivity in the region of the longitudinal center plane, and the transmissivity gradually decreases in the direction towards the outlet slits 37. As a result, the radiation intensity of the UV light impinging onto the surface of the substrate 2 can be adjusted such that it is highest in the vicinity of the longitudinal center plane, where the concentration of radicals is lower compared to the region directly beneath the outlet slits 37, and decreases transverse hereto. Hence, despite the inhomogeneous distribution of radicals, a widened region providing a substantially homogenous removal of lacquer may be provided. Even if a reduced concentration of radicals may not be fully compensated for, as substantial homogenization over the case as shown in FIG. 9b may be achieved. Thus, despite a changing concentration of radicals, a substantially homogenous process result may be set over the width of the opening 21 in the main body 20, as shown in the graph of FIG. 9c . As such, a substantially homogenous high amount of lacquer removal is provided over the width of the opening 21 in the main body 20.

A corresponding effect can be achieved by the material of the tube element itself, or by a coating or a foil on or adjacent to the respective region of the tube element. In the latter case, a coating or film should preferably be arranged inside the tube element in order to avoid any contamination of the liquid and also to be able to neglect the resistance of the coating to the media being used.

In FIGS. 10a to 10c further configurations of the radiation member 18 are shown, wherein in each case again the housing 14 having chamber 22 and supply line 24 is indicated only schematically. Also again, a substrate 2 is shown schematically. Graphs as shown in FIGS. 9a to 9c are not shown in FIG. 10.

In the configuration according to FIG. 10a , again a single radiation source 32 is provided which is accommodated in a tube element 30. In this configuration, a reflective coating 31 is provided on the portion of the tube element 30 lying inside the chamber 22. This can be designed, for example, as a layer or foil attached to the tube element, which may for example be attached to the inside or the outside. This layer of foil can be fully reflective for the radiation emanating from the radiation source 32 or it can be reflective only in certain wavelength ranges. In FIG. 10a , the shape of the reflective coating 31 is shown in a simplified manner to follow the contour of the tube element. However, the shape may deviate in this respect, wherein the shape should be specifically designed such that the intensity of the radiation exiting from the tube element 30 in the regions adjacent to the outlet slits 37 is lower than in the region of the longitudinal center plane C and in particular in substance steadily increases towards the longitudinal center plane C. Hence, the intensity of the radiation exiting from the tube element 30 is highest in the center (in the vicinity of the longitudinal center plane C) and decreases transverse hereto.

FIG. 10b shows a further configuration of a reflective coating 31, wherein here another shape of reflective coating 31 is shown, which in an upper region is flat and in section forms a chord to the round shape of the tube element. Such a shape makes it possible to provide a further radiation source (not shown), in particular in the upper region of the tube element 30 (above the reflective coating 31). This further radiation source could emit in a different spectral range than the radiation source 32 in order to provide different radiation in the region of the flow channel compared to radiation directed towards the region of the outlet slits 37 and in the direction of the substrate 2. In addition to a homogenization of a process result, such as a removal of lacquer (by means of adjusting a specific ratio between the radiation locally impinging onto the substrate and the local radical concentration), a wavelength selection (providing radiation with different primary spectral ranges in different regions of the device, in particular within the chamber 22 and outside the body) could also be provided here.

This could also be achieved via selective reflection characteristics of the reflective coating 31, which, for example, may allow UV radiation at a wavelength below 200 nm to pass and may substantially reflect UV radiation at a wavelength above 200 nm. Of course, this also applies to the embodiment according to FIG. 10 a.

In both cases, that is in the configuration according to FIGS. 10a and 10b , it is also possible to achieve a wavelength selection by arranging additional radiation sources within the body 20 in such a way that they emit from outside into the chamber 22. In this case, the radiation emitted into the chamber 22 could for example be primarily in the range below 200 nm, for example at approximately 185 nm. The radiation emitted out of the chamber 22 via the opening 21 could in particular be primarily in the range above 200 nm, for example at approximately 254 nm. While the radiation below 200 nm may primarily serve to decompose the medium in the flow channel, the radiation above 200 nm may primarily serve to generate radicals.

In addition to a specific spatial distribution of the radiation intensity, an additional wavelength selection could easily be achieved by the above configurations, which provides a different radiation within the flow chamber compared to the radiation emitted out of the chamber in the direction of the substrate 2.

Also in this case the reflective coating 31 or mirror element should be specifically designed such that the intensity of the radiation exiting from the tube element 30 is highest in the vicinity of the longitudinal center plane C and decreases transverse hereto.

The embodiment according to FIG. 10c may also achieve similar effects. In this embodiment, the radiation part 18 again has a tube element 30. Within the tube element, a first radiation source 32 is provided, which may be of the type described above. Below the first radiation source, a concave, upwardly curved mirror element 200 is provided which substantially reflects radiation emitted by the radiation source 32 back upwards. Below the mirror element 200, an arrangement of different second radiation sources 210 is provided. In particular, seven radiation sources 210 are shown. These radiation sources 210 each emit at least light in the UV range at different intensities. In particular, the intensity decreases steadily from the middle one of the radiation sources 210 to the outer ones of the radiation sources 210. That is, the outermost radiation sources 210 emit light with the lowest intensity. With this configuration, again a desired intensity distribution of light exiting from the tube element 30 may be achieved such that the intensity of the radiation exiting from the tube element 30 is highest in the vicinity of the longitudinal center plane C and decreases transverse hereto.

In particular, over the width of the opening 21 in the body 20, a substantially uniform process result, such as a removal of lacquer (by means of adjusting a specific ratio between the radiation locally impinging onto the substrate and the local radical concentration), with the aforementioned advantages can be obtained. In addition, this configuration also allows a certain wavelength selection such that radiation emitted into the flow space can have a different spectral range than radiation emitted out of the opening 21.

For example, the first radiation source may again emit in a range below 200 nm, for example at approximately 185 nm, while the radiation sources 210 for example emit radiation in a range above 200 nm, in particular at approximately 254 nm.

FIGS. 11 and 12 show still further configurations of the radiation part 18. Again, the body 20 with the chamber 22 and the opening 21 and a substrate 2 are schematically shown.

The radiation part 18 in the configuration according to FIG. 11 again has a tube element 30 which is substantially transparent to UV radiation. Within the tube element 30, two radiation sources 220 and 222 are shown. The two radiation sources 220, 222 are arranged one above the other within the tube element 30. The radiation sources 220, 222 are of different types, and in particular emit in different spectral ranges. Hereby, the upper radiation source 220 for example emits radiation primarily in a spectral range below 200 nm, for example at 185 nm, while the lower radiation source 222 emits radiation primarily in a spectral range above 200 nm, for example at 254 nm.

Between the radiation sources 220 and 222, a curved reflector 226 is provided, which is reflective on both sides. The reflector essentially causes a separation of the radiation which is emitted into the flow space from the radiation which is emitted out of the opening 21. The reflector 226 is arranged such that radiation is emitted from both the upper radiation source 220 and the lower radiation source 222 into the end region of the respective flow channels adjacent to the outlet slits 37.

While the radiation below 200 nm, as mentioned above, primarily serves to substantially cause decomposition of the medium in the flow channel, the radiation above 200 nm serves to generate radicals. Since a generation of radicals is already desired in the end region of the flow channel, the configuration as shown is advantageous. The curvature of the downward-pointing region of the reflector 226 may be specifically selected in such a way that again a desired ratio between the radiation locally impinging onto the substrate and the local radical concentration may be achieved over an area which is as wide a possible, which ratio enables homogenous processing. Here, the ratio changes such that with a decreasing racial concentration the intensity of the radiation increases, as described above. In particular, the intensity of the radiation is highest in the vicinity of the longitudinal center plane of the arrangement and decreases transverse hereto.

In the embodiment according to FIG. 12, once again a tube element 30 with two radiation sources 220, 222 is provided, which like in FIG. 11 may emit in different spectral regions. It is also possible to dispense with the upper radiation source 220. Again, a mirror element 240 is provided in the tube element 30. The mirror element has a stylized M-shape, as can be seen in FIG. 12, wherein the lower radiation source is arranged within the M-shape, while the optional upper radiation source 220 is arranged above the mirror element. In particular, the mirror element has two spaced apart, substantially parallel first legs 241. At the upper ends of each of the first legs, a second leg 242 is provided, the second legs 242 being angled inwards. At the upper ends of each of the second legs 242, an inwardly extending third leg 243 is provided. The third legs 243 are arranged in the same plane and extend substantially parallel to each other and perpendicular to the first legs 241. At the inner ends of each third leg, a fourth leg 244 is provided, which extend inwardly at an angle with respect to the third legs 243 and which meet in the center between the first legs 241. The respective angles between the first legs and second legs, between the second legs and the third legs and between the third legs and the fourth legs is in each case larger than 90°. The respective second leg, third leg and fourth leg form a roof shape, as shown. The mirror element 240 is arranged in the tube element 30 such that the first legs are substantially parallel to the longitudinal center plane of the arrangement and that the mirror element is symmetric to the longitudinal center plane of the arrangement. As shown in FIG. 12, the mirror element 240 is arranged such that radiation of the second radiation source 222 at least partially reaches the chamber 22 and in particular the area adjacent to the respective outlet slits 37 of the chamber 22. Alternatively of additionally an additional reflector may be provided in the arrangement as shown in FIG. 12, which is for example arranged above the first radiation source and which prevents that radiation is directly emitted towards the area of the supply line 24. In particular, such a reflector could extend over a larger area and could direct the radiation specifically in the towards the outlet slits 37 or a region of the chamber 22 adjacent to the outlet slits 37.

In this configuration, again a desired intensity distribution of the light exiting the tube element may be achieved, such that the intensity of the radiation exiting the tube element is highest in the vicinity of the longitudinal center plane of the arrangement and decreases transverse hereto.

The operation of the device 1 will now be explained in more detail. It is initially assumed that the configuration according to FIGS. 1 and 2 is present. The operation does not change for the different embodiments.

The application unit 6, in particular the main part 8, is brought into a position adjacent to a substrate 2, in which liquid emerging from the opening 21 does not get onto the substrate 2. Via the media ports 16, a liquid medium, for example, diluted hydrogen peroxide water or ozone water O₃—H₂O, is introduced into the chamber 22, while at the same time the radiation source 32 is switched on.

In the flow chamber between tube element 30 and inner wall 23 of the chamber 22, a flow of liquid builds up, which is accelerated in the direction of the outlet slits 37. In particular, the velocity of the liquid is accelerated from an overhead region at the end of the supply line 24 to the outlet slits by a factor in the range of 10:1 to 40:1, and preferably by a factor in the range of 15:1 to 25:1, by means of a corresponding change in cross section.

Below the main part 8, a curtain of water forms, which extends uniformly over a substantial part of the length of the main part 8. The radiation emitted by the radiation source 32 decomposes the liquid in the flow channel, that is between the supply line 24 and the outlet slits 36, to destroy unwanted reactive species within the liquid. At the same time, radicals are generated in the liquid by the radiation. These mechanisms primarily take place at different spectral regions of the radiation. For the decomposition, radiation in a spectral range below 200 nm is advantageous, while for radical generation, radiation above 200 nm, in particular at approximately 254 nm, is desired. Without special measures, as described in FIGS. 9 to 11, the radiation emanating from the radiation source 32 in the region of the flow channel and outside the body 20 is substantially the same and generally contains radiation components both above and below 200 nm. Due to the acceleration of the flow in the flow channel, a homogenization of the flow is achieved and thus the liquid curtain is formed homogeneously over a large width.

As described, in the flow channel, on the one hand, the liquid is decomposed and unwanted reactive species are broken up while at the same time radicals, in particular hydroxyl radicals, are generated. These radicals are generated in particular also in the region of the outlet slits 37 so that they can exist for a sufficient time to reach the surface of the substrate 2, when the main part 8 of the application unit 6 is subsequently moved over the substrate 2.

The substrate 2 may for example be a photomask, having residues of lacquer or resist thereon that must be cleaned off. Such a cleaning can be performed over the whole area of the photomask or only over certain areas of the mask. By moving the main part 8 of the application unit 6 over the substrate, the liquid curtain is moved across the substrate 2. The radiation source 32 continuously generates radicals within the liquid, wherein a respective generation of radicals in particular in the region of the outlet slits and below the opening 21 in the body 20 is of importance and the generation of radicals may be concentrated here by certain measures as described in the embodiments. Thus, the liquid is charged with radicals underneath the opening 21 and is particularly effective for the cleaning off of lacquer or resist.

Hereby, in particular when using ozone water O₃—H₂O an increased concentration of radicals may occur directly beneath the outlet slits 37, which decreases transvers thereto, as indicated in FIG. 9b . In addition to the liquid, which is charged with radicals, also a portion of the UV radiation of the radiation source 32 reaches the surface of the substrate to be treated, wherein the radiation further activates the surface and facilitates a respective cleaning by means of the radicals. Hereby the intensity of the radiation locally impinging onto a surface area of the substrate should be in a desired ratio to the local radical concentration in order to compensate for inhomogeneities in the concentration of radicals occurring over the width of the opening 21. In particular where the racial concentration is locally lower a higher intensity of the radiation impinging onto the surface of the substrate to be treated should be provided. In particular, in accordance with the invention, it is provided to influence the radiation exiting the opening 21 through the tube element 30 such that the intensity of the radiation increases towards the longitudinal center plane of the chamber 22. In regions which are not directly beneath the opening 21, the liquid has a rapidly decreasing concentration of radicals, since the radicals rapidly disintegrate, wherein the decreasing concentration of radicals in combination with a low intensity of the UV radiation in these regions leads to a rapid decrease in the effect onto the substrate. The process is most effective beneath the opening and may be homogenized over the width of the opening by means of a respective adjustment of the intensity of the UV radiation to the concentration of radicals.

The speed of sweeping of the liquid curtain over the substrate can be matched to the required cleaning performance to achieve sufficiently long residence times of the radical-charged liquid on the substrate. When the mask is cleaned accordingly, either the media supply can be stopped and the radiation source switched off, or a next substrate 2 can be treated in a corresponding manner.

The invention has been explained in detail above with reference to preferred embodiments of the invention, without being limited to the specific embodiments. In particular, the different features of the embodiments can be freely combined or exchanged with one another, provided that they are compatible. 

The invention claimed is:
 1. An apparatus for applying a liquid medium irradiated with UV radiation onto a substrate, the apparatus comprising: a housing having an elongated chamber, at least one inlet opening, which opens into the chamber, and at least one slit shaped outlet opening opposite the inlet opening, which extends over the length of the chamber; a tube element, which extends in a longitudinal direction through the chamber, the tube element being at least partially transparent to UV radiation, wherein the tube element is arranged in the chamber such that a flow space is formed between the tube element and the wall of the chamber, the flow space being symmetric with respect to a longitudinal center plane of the chamber, the longitudinal center plane dissecting the outlet opening in its middle, and such that the tube element extends into the slit shaped outlet opening in the housing and thereby forms two longitudinally extending outlet slits between the tube element and the housing; at least one UV-radiation source in the tube element, which is arranged to emit UV-radiation in the direction of the flow space and through the outlet opening out of the housing in order to generate radicals in the liquid and to bring the radicals to the surface of the substrate; and means provided in or on the tube element for adjusting the radiation exiting the outlet opening through the tube element such that the intensity of the radiation increases towards the longitudinal center plane of the chamber, wherein the means for adjusting the radiation comprises at least three second UV radiation sources located within the tube element, adjacent to each other and adjacent to a portion of the tube element which is arranged in the outlet opening or outside the chamber, wherein the adjacent second radiation sources emit UV radiation with different radiation intensities.
 2. The apparatus of claim 1, wherein the tube element has a round cross section and the means for adjusting the radiation exiting the outlet opening comprise at least one optical element arranged to vary the intensity of the radiation exiting the tube element such that the intensity steadily increases towards the longitudinal center plane of the chamber.
 3. The apparatus of claim 2, wherein the at least one optical element comprises at least one mirror element which is arranged adjacent the radiation source and which reflects radiation toward the outlet opening.
 4. The apparatus of claim 3, wherein the mirror element is symmetrical with respect to the longitudinal center plane of the chamber.
 5. The apparatus of claim 3, wherein the mirror element at least partially encompasses the at least one radiation source.
 6. The apparatus of claim 3, wherein the at least one radiation source is arranged on the longitudinal center plane of the chamber and below a transverse center plane of the tube element, which extends perpendicular to the longitudinal center plane of the chamber and dissects the tube element in the middle, and wherein the mirror element is at least partially arranged underneath the transverse center plane of the tube element.
 7. The apparatus of claim 1, wherein the at least one radiation source is arranged on the longitudinal center plane of the chamber and below a transverse center plane of the tube element, which extends perpendicular to the longitudinal center plane of the chamber and dissect the tube element in the middle.
 8. The apparatus of claim 1, further comprising at least one separating element in the tube element, which essentially blocks radiation of the second UV radiation sources in the direction of the flow space.
 9. The apparatus of claim 1, wherein the at least three second UV radiation sources are arranged to emit UV radiation only through the outlet opening. 